I'm a little confused about what actions characters can take when they're engaged in melee.
Two examples from my latest session:
1.) The PC assault marine is engaged in melee with a horde of hormagaunts and he wants to use his jump pack to jump straight up and then perform a charge straight down so he can get the magnitude bonus from Wrathful Descent. So far I've been letting him do this, but granting the horde a free attack on him. This doesn't quite feel right as the AM could potentially take a lot of damage for trying to inflict only an extra d10 of magnitude damage. On the other hand I don't want him to get away with it scott free.
2.) The PC devastator has been charged by a horde of hormagaunts but on his turn wants to fire his heavy bolter at the Tyranid warrior behind the horde. I know that on p.247 of the core rulebook it says that characters in melee can only take actions with the melee subtype, but technically a character is only engaged in melee if he and his target are adjacent. Since his target is behind the horde just shooting at the warrior with no penalty seems completely legal by RAW, unless there are rules for shooting out of melee or moving out of melee that I've overlooked.